Propeller.



1 G. T. A. H. WIEDLING.

PROPBLLER.

APPLICATION FILED JUNE 12, 1908.

Patented M11122; 1915.

v vwentoz W e n .1 n a -S 1 7n 13M714 a e o 0. T. A. H. WIEDLING.

PROPELLER.

APPLICATION FILED JUNE 12, 1908.

Iatented Mar.2,1915.

a SHEETS-SHEET 2.

G. T. A; H. WIEDLING.

PROPBLLER.

APPLICATION FILED JUNE 12, 1908.

Patented Mar. 2, 1915.

3 SHEETS-SHEET 3.

CARL THEODOR AUGUST HERMAN N ,WIEDLING, OF NORTH BERGEN TOWNSHIP, HUDSON COUNTY, NEW JERSEY, ASSIGNOR TO THE WIJEDLING MANUFACTURING COMPANY, OF NORTH BERGEN, NEW JERSEY, A CORPORATION OF NEW JERSEY.

PROPELLER.

Specification of ll'iettersi-Patent. Patentedl' lwart 2, 1915.

Application filed June 12, 1908. Serial No. 438x037.

To all whom it may concern Be it known that I, CARE Ti-inonon Ao- GUST HERMANN WIEDLING, a citizenof the new and Improved Propeller, of which the following is a full, clear, and exact de scription.

The invention relates to rotary propellers for ships, balloons, flying machines and similar vehicles, and it is also of equal usefu1- ness for other devices and machines, as a rotor for steam, Water or other fluid turbines, pumps, air compressors, blowers, fans, etc.

The object of my invention is to secure a greatly increased power eliiciency and to reduce vibrations.

To enable others skilled in the art to make and use my invention, T will now describe it, by reference to the accompanying three sheets of drawings, in which-- Figure 1 is a stern view of my propeller as it would appear when installed for the propulsion of a ship or flying machine; Fig. 2

is a view, 111' plane development, of. one of the blades of my propeller, with four blades,

' giving the correct least widths'required and by-the line XX, and it further shows, in

as found by calculation; Fig. 3 is a view, in

plane development, of one of the blades 'of' my propeller, with four blades, wherein the widths at the different radii, are made twice as great throughout as those in Fi g. '2, and

which corresponds 1n size, to the blades shown in all the figures, except those of Figs. 2 and 5; Fig. 4 is a starboard View of my propeller, in which one half of the stationary shrouding is removed and shown section on dotted line Y.Y, of Fig. 1; ig. 5 shows, in plane development, the cross-section of the propeller bladeat the outer radius and corresponding to the least blade widths required, as per Fig. 2. It also shows the degree of the angular position of this blade section, in reference to the axis of the propeller, the direction of which is indicated plane development of the co-axial cylindrical crossfsection, the area of the'water current, which is sub ect-to dynamic pressure;

Fig. 6 is a diagram, showing in plane development, the cross-sections of the propeller blade, at the different radii from the axis of the propeller, as indicated by the circular arcs 3, at, 5, and 610 in Fig. 1. -It also shows the degree of the angular position of these sections, in reference to the axis 'of the propeller, the direction of which is indicated by line X-X, however, Without showing them n their true, relative position. Further, Fig. 6 shows, in plane development, the co-axial cylindrical cross-sections,-

of the water current, which are subject to dynamic pressure and which pertain "to the blade sections at the different radii; Fig. 7 is a diagram of the dynamic pressures, genrent, within the entire range ofthe driving face of the propeller blade and throughout of the different distances from the driving face of the blade and at the different radii of the propeller and at the co-axial cylindrical, cross-sectional areas of dynamic pressure, pertaining to the different blade sections.

This diagram refers particularly to the wide blades adopted in Figs. 1, 3, 4, 5, 8 and 9, and not to the blade of least width, shown in Figs. and 5; Fig. 8 is a diagram, in plane development, of the'cmaxial cylindrical sections through thedriving face of the blade, at the different radii. and explains the method used for locating the blade sec- I .tionsaxiallv and circumferentially; Fig. 9

erated by the deflection, of the water cur- I 'in active range of the driving face of the blade. This radial motion, in properly proportioned propeller blades, is almost entirely due to the dynamic pressure generated by the deflection of the water current, and only to a very slight degree due to centrifugal action caused by the rotation of'the Water with the propeller, contrary to the ordinary supposition. Loss of efficiency of a lesser degree is also due to the friction of the water current on the propeller'blades, particularly when the latter are made of a much greater width, than required, either for strength or efl'ect. Other losses are caused by the faulty cross-sectional form ofthe blades, either by the use of blades of true anduniform pitch, surface, 'or'through the faulty curvature of the driving face of the blade or the back thereof, or bythe wrong form of the leading edge of the blade. a v

I have found through experimental and mathematical research that the ideal propeller is one in which the stream lines of the water current while within the range of action' of the driving face of the blade are guided Within lines of constant distance from the axis of rotation of the propeller,

or within cylindrical surfaces concentric with the axis 'of the propeller. Further, in this manner I have found that for maximum eificiency the pitch at the leading-edge of the propeller blade must be equal at all the radial distances from the axis of rotation; further, the pitch velocity at the leading edge of the blades must be'made equal to the relative axial velocity of the Water current so as to lead the latter into perfect tangential contactwith the driving face of the blade. By pitch velocity I mean the velocity with which any point though sta- The widths of the blades, the" circumferential widths and the relative widths of. the .water current, the radii of curvature of the driving face of the blade, all are straight line measurements, taken within the plane development of these co-axial cylindrical cross-sections. The conditions set forth herein, are those required for the maximum performance and quietness of running of my propeller and thereforafthe pitch velocity,

at the leading edge of the blade, is assumed as equal to the. axial velocity of the water current, relative to the propeller. Thereby the Water current enters the normal plane of the propeller at an angle, which is equal to the pitch angle, X, at the leading edge of the driving surface of the blade. F urther, herein is assumed, as is the general practice, that the blades, of the propeller, are spaced equidistant circumferentially, and that they are located within the same normal axial plane and that they are of the same size and form. Under the term circumferential'width of the water current, acting upon one blade, I mean the distance, in circular measurement, within a plane normal to the axis of the propeller, of similar points of the leading edges of two adjacent blades and of the same radial distance from the axis of the propeller. The total circumferential width of the water current, at any radius, 'r', of the propeller, is lr'r, and therefore the circumferential width, 10, of the water current acting upon one blade of the propeller, having n, number of equally spaced blades, is equal to the total circumferential width of the water current, di-

vided by the number of blades, or

Under the term, relative width of the water current, I mean the width thereof, as measured within the plane development of the co-axial cylindrical cross-section, at any radius of the propeller and normal to the driving face line. This is the normal distance between the tangents, of thedriving face lines, at theleading edges of two adj acent blades, as measured within the plane development of the co-axial cylindrical cross-section pertaining to any radius of the propeller, because the water current enters between each two adiacent blades obliquely, at the pitch angle, X, of the leading edge of the blade. Therefore, the relative width, W, is a function of the circumferential width of the water current, acting upon one blade, and the pitch angle, X, of the leading edge of the blade, or

Further, I have found that the blades of the propeller-must be made of a pitch increasing uniformly from the leading edge to the ,rear edge, or, in other words, the driving face of the blades must, in any coaxial cylindrical crossssection concentric with the axis of the propeller, appear in balance the dynamic pressures. in the difwere plane-development thereof as a true circular curve. Further, I have found thatthel degree of curvature of the driving face of the blade in co-axial cylindrical cross section thereof, as afore mentioned, affects the performance of the propeller greatly, and that the radius of curvature thereof must be at least equal to the'relative width of the water current passing between two adjacent blades, whereby the relativewidth of the Water current is measured on a line normal to the cross-sectional line of the driving face of the blade. On this basis I have found that very efficient propellers can be constructed with comparatively very narrow blades, and that, in most cases, the blade Widths must be'selected rather for the purpose of sufficient strength and keenness of cross-section than for the purpose'of gripping the water current. Further, I have found that by means of the correct selection of the curvature of the driving face of the in the co-axial cylindrical crosssections thereof, the dynamic pressures generated through the deflection of the water current can be augmented or increasedorreduced and controlled so as to very closely ferent layers of the water current, in radial direction. Further, I have found that the pressure generated through the 1 deflection of the water current primarily acts in the direction normal to the cross-sectional cur.- vature of the blade, and thaton this account the blade may be curvedin a combined cir cumferential and axial direction so as to completely prevent the passage of water to ward the axis of the propeller. Further, I have found 'a novel and correct form of shrouding, of the leastfrictional area, however of suflicient area to completely prevent the escape of water from the current under dynamic pressure to the outside of the cir-.

cumference of the propeller. Finally, I have combined these features of my, invention intoa very. practical form of a propeller, which: is adapted to suit all conditions found ingeneral practice.

In all of the drawings, except, in Fig. 7, the'figures of reference from 0 to 10 indicate the relative radial distances of the blade sections from the axis of rotation of the propeller. In Figs. 1 and 4, 11 is they stern frame and 12 the stern bearing of a ship,

flyingmachine or other device to be driven by the propeller 21. The propeller shaft 22 is journaled within the stern bearing 12 and is'secured on its outer and within the hub 23 of the propeller. The hub 23 has on its rear face the cap 13 to prevent cavitation on the back face thereof, and is provided, in that embodiment of my invention illustrated, with the. four propeller blades 24, each of which has onitsouter edge a shredding 25, of cy- .lindrical curvature corresponding to, the

outer radius of the propeller blade.

Concentrically surrounding the. propeller andattachedto the branches 26, 26, of the stern frame 11 is located the stationary cy formly increasing pitch so as to give a pitch of 2.23 times the outer diameter ofthe pro-' peller at the rear edge of the blades, and,

therefore, a mean pitch ratio .of 1.88. The

meanpitch ratio is obtained from the mean. pitch angle of the outer cross-section of the driving face of the blade, The pitch ratio of 1.57 at the outer leading edge of the blade.

corresponds toa pitch'angle of26 83 10"; the pitch ratio of 2.23 at the rear outer edge of the blade corresponds to the pitch angle of 35? 22 6.. rTherefor e, the meanpitcb. angle of the outer edge ofthe driving face of the bladeis 30, 57, 38", to which corres sponds the pitch" ratio of 1.88, which is the 1 left hand of Fig. 1 indicates the direction of rotation of the propeller for the forward motion of the ship. The blades 24 of the propeller are curved in a helically pitched spiral of opposite helical and opposite spiral pitch to the pitcli of the driving face of the propeller blades, as is evident in Figs. 1' and 4; or, in other words, the blades of the propeller with driving faces of left-hand pitch,

as shown herein, are curved in a helically pitched spiral of right-hand helical and right-hand spiral pitch Otherwise, in a propeller having driving faces of right-hand mean pitch ratio. The arrow on the upper pitch, the blades are curved in a helically pitchedspiral of lefthand helical and lefthand spiral pitch. By a helical pitched spiral is understood a line generated by the progressive rotation of a point around the axis of the propeller, which point contemporarily increases its distance from'the said axis. By right-handspiral pitch is understood the direction of theline generated by the progressive clockwise rotation as seen from the-stern of the vessel, of a point around the axis of the propeller, with a-constantly increasing distance from the axis. Likewise, by left-hand spiral pitch is understood the direction of a line generated by the progressive counter-clockwise rotation as seen from the stern of the vessel, of a point around the axis of the propeller with a simultaneously increasing'distance from the axis of the propeller. I

IV have found that the ideal propeller in which the water current is not'subject to centripetal or centrifugal motion, requires very-narrow blades only to completely and.

perfectly act on the water passing through the propeller. In a four-bladed propeller of the pitch shown in Figs. 1 and 4, and mentioned dimensionally hereinbefore, the ideal blade would have to be of a width of 0.056

times the outer diameter of the propeller at its widest part, near radii? and 8 of Fig. 2, in which the ideal blade widths are indicated in decimal fractions of the outer diameter of the propeller.. However, these narrow blades can in most cases not be used actually for the reason of lack of strength, or otherwise, when made 'sufliciently strong would lack of the keenness of cross-section,

which is so very essential in good propeller design. Therefore, and for another very important reason, which is stated hereafter, I have selected for the blades of the propeller shown herein, a width which is a multiple throughout the different radii of the least widths shown in Fig. 2.

Fig. 3 shows, in plane development, one of the blades of the propeller of double the width throughout of the different radii, as that of Fig. 2, and of the width adopted in Figs. 1, 4,6, 8 and 9 of the drawings. The diagram, Fig. 5, shows in plane development of the co-axial cylindrical crosssection, the ideal propeller blade l0-28,

corresponding to the least width, at radius 10, of Fig. 2. The driving face 29 thereof is of the circular curvature described by radius 28-30, which latter'is made equal to the relative width of the water current, asmeasured normally to the are 1028, of

r the driving face 29 of the blade section. Therein the sector-10, 28,30, represents the of circular curvature, of a radius equal to or less than-the relative'width of the water current pertaining to the blade section, that the pressure generated within the sectorial area of dynamic pressure is equal or very *nearlyequal throughout the said sectorial area of dynamic pressure. Therefore, in the diagram, Fig. 5, the pressure generated within the sectorial area 10, 28, 30 of the water current is equal'throughout the saidu area. In the propeller of that description I prevent the radial outward flow. of the water completely by providing the blade of the propeller at its outer edge with a shrouding corresponding in form and area to the circumferential area of-dynamic pressureor to the sectorial surface 10, 28, 30, Fig. 5. However, in this propeller the circ'umferential areas of dynamic pressure, cor responding to the smaller radial distances. from the axis of rotation of the propeller, are subject to considerably less dynamic pressure than those of larger radius, overlapping them, and thereby the water current within the'range of the driving face of the blade suffers considerable deflection from its true path of constant distance from the axis of the propeller by flowing toward the areas of lower pressure located nearer to the axis of rotation of .the propeller. To materially reduce these deviations of the water current from the lines of constant distance from the axis of the propeller, I curve the propeller blade in a helically pitched spiral of opposite helical and opposite spiral pitch to the pitch of the driving face of the propeller blade. Thereby the areas of greater dynamic pressure are radially supported by the driving face of the blade, and the centripetal motion of the water current is considerably reduced andthe power elliciency and thrust pressure o'f the propeller are thereby materially increased. To further increase the efliciency of my propeller, I reduce the curvature of the driving face of the blade in the co-axial cylindrical crosssections by making the radii of curvature a .multiple of the relative widths of the water current. This is explained by means of the diagram, Fig. 6,;which represents, in plane development, the co-axial cylindrical cross-sectionsof the propeller blade and of the cross-sectional areas of the water current under dynamic pressure, which correspond to the radii indicated in Fig. 1 by the reference figures 3, 4, 5, 6, 7, 8, 9 and 10, and to like blade sections similarly numbered and shown dotted in one of the propeller blades of Fig. 4. In Fig. 6 the radii .of curvature of the driving faces of the blade sections are equal throughout to twice the relative width of the water current pertaining to each blade section, and the blade is made twice as wide throughout the different radii as the ideal blade of least width, of Fig. 2; it', however, is of the width shown in Figs. 1, 3, 4 and 8, so as to deflect the water current in the same degree as the ideal blade of Fig. 2. In Fig. 6 the cross-sectional areas of dynamic pressure appear as truncated sectors, of which 33, 34, 35, 36, is the outer area of dynamic pressure, pertaining to blade section 10, and showing at the same time the true form and size of the shrouding 25 of the propeller blades of Figs. 1 and 4. Similarly the truncated sector 37, 38, 39, 40, represents. the crosssectional area of dynamic pressure, as pertains to blade section 9. It must be noted, however, that Fig. 6

lit)

. medium by j, and the earnest is only adiagram, for the graphic determination of the angular position of the blade sections in reference to the axle of the.

propeller, the direction of which is indicated pressure generated through the deflection of the water current is not equal throughout the surface of each sector, like in the full sector area 10, 28, 80, of Fig. 5, but decreases gradually from the driving face; of the blade toward the apex of the truncated sectors, although the dynamic pressure is practically constant within each of the stream lines of circular curvature, concentric with the arc of curvature, of the driving face of the blade. Proof of this is as follows: Let the radius of curvature of the cross-sectional line of the driving face of the blade be denoted by It, and any lesser radius of curvature of a stream line of the water current within the same area of dynamic pressure by R; the radial distance of the area of pressure from the axis of the propeller by r, the velocity of the water current relatively-to the blade section by V,-the density of water or other acceleration due to gravity, by 9'. Suppose a fine jet of water of the width dlt, and of the radial thickness dr, and of rectangular cross-section, enters the surface of the propeller blade tangentially'at 28, Fig. 5, with the velocity V,

tit)

and passes frictionless with uniform velocity along the are 28, 10, and is discharged tangentially at the edge of the circular are 28, 10, Fig. 5. By this, each particle of water is subjected to centrifugal action,

jet normal to the are 28, 10, is then on radius R, and on a shorter are 28, 10

on the cylindrical surface I thereof, or

forms a circular is subjected to greater centrifugal action in I inverse ratio of the radii, or as R, The

total centrifugal pressure in the latter case on the are 28, 10 is therefore,

Cp= Xarc 2,8, IOX'dRXdrX 7'. (II) However, the quotients are 28,10

and

'arc28, 10

are equal and constant because the length of the arc diminishes in the same ratio as 1ts radius. Therefore, the total centrifugal pressure C70 of any similar et of the width (ZR, and of any radius R is constant, or

Hence, the total centrifugal pressure Up on the are 28, 10, due to the whole water current of the width R and the radial thickness dr is:

V R OZ7== QXdTXMTJ 28,10}; (1R9 v Op= iXdrXarc 28,10. (IV) From the latter equation we get the dynamic pressure per unit area, p, which cZrXarc 28, 10,

by dividing the right-hand side of this equation with the area drX are 28, 10,

. Up V .drXarc 28, 1o drX-arc 28, 110 g 'drxarc 28, it)

or j

By means of Equation (lllll) it is proven that each (ZR of the water current, no matter what the radius of the curvature of its motion, adds an equal increment of pressure on the surface,

are 28, 10x0.

Therefore, the .unit pressure generated by acts of the blade. Denoting the radial width of the'current and the radius of curvature of R, which is greater than the widthR of the water current. The same result is had by integrating Equation (III), between limits R and R, and dividing by the area,

the cross-sectionalzline of the driving face the'water current with R, and the dynamic 't th' h pvleisglra: per 1 1m area, 1n 1s case, w1t p 1 drxarc 28, 1O

, V R whereby Y Z e- R (v1) I Y R g or the radius of curvature of the stream line which 1s the dynamic pressure'per unit area of the water current at the apex-line of trunof the driving face of the propeller blade,

cation, of the truncated area of pressure, of a cross sectlonal curvature of the radlus Fig. 6. In this way R I I R r V, are 218,10 aro 2 l I- 0 o P g arc 28, lO'xdr 5 6, is zero and increases from there toward V are 28', the driving face ofthe cross'sections of the P 7 m)' .blade in a ratio set forth in the equilateral hyperbolical curves of the diagram of dyr namic pressures, Fig. '7. Thevelocity V, m are 28, 10 R the preceding equations, is. the resultant of are 28, 10 R the circumferential velocity and the pitch therefore velocity of the leading edge-of the propeller I as components. Denoting the radial (lis- J(1 tance of any element from the axis of the 9 propeller with 1', as before, the number of and turns per second, at which it is driven with R R R N; the constant axial pitch at-the leadrn y edge of the driving face with T; the axia pitch velocity with 'v, and the circumfer- =KJ( 'EE@)=Y JBQ V ential velocity of any element of the leading 9 B 9 R edge of the blade with c, we find;

The above, (VI) is the equation of an c=N2nr (VII) equilateral hyperbola, in reference to one of 'v= NT (constant) (VIII) the asymptotes and a line parallel to the and other asymptote as axes. By means. of T 2 3 Equation (VI) 'the dynamic pressure p 1 within any stream. line of the truncated or areas of dynamic pressure of Fig. 6 can be calculated, by inserting for R the distance 1 or V m) ture of the stream line.

pressure on the driving face 28, 10. Through of the stream line, from the apex line of truncation and for R, the radius of curva- Otherwise, for the purpose of generating a predetermined dynamic pressure on the driving face of the propeller blade, the pressure p and the width of the water current R must be inserted in this equation, for finding the corresponding radius R of the cross-sectional curvature of the driving face of theblade. The equilateral hyperbolical' curves, 3 -3, 4--4, 55, etc., of the diagram of pre ures, Fig. 7, have been calculated in this In nner.

' Through Equation (V) it is evident that the dynamic pressure in the full sector area, 28, 10, 30, is equalthroughout thereof and the pressure at the apex 30 is the same as the V=N /(2m") +T (IX) because 0 and u act at right angles. Inserting the value of V, of Equation IX, in Equation VI, we have Denoting the number of uniformly spaced propeller blades with n; the pitch angle, at the leading edge of the driving face of any co-axial c lindrical cross-section thereof with X; t e circumferential Width of the Water current, within a plane normal to the axis of the propeller and pertaining to the blade section at r, with w and the relative width of the water current, measured normally to the leading edge of the blade section with R,;, as before, then,

Equation (VI) it is demonstrated that the dynamic pressure at the apex line of truncation of the areas of dynamic pressure, Fig.

1 matte" 7 W -V 7 Substituting the above value of R in Equation VI", We have J 2m '1 I Z 2 2 2 p N 9 RJdfi7+T The latter equation gives the dynamic pressure per unit area, of the driving face of the blade, for any value of the radius of curvature R, thereof and when R is made equal to R the relative Width of the Water current, then p, will be the dynamic pressure per unit area of the driving face of a least Width and radius, as shown in Figs. 2

"and 5'. In that case Equation Vl will read u ge-W T v a The dynamic pressure per unit area of the driving face of the propeller, in which the radius of curvature of the cross sections of the blade is made a multiple, m, of the least width of the Water current, as in Figs. 1, 3, 4, 6 and 8, may also be found by multiplymg the right side of Equation V1 with the quotient 57, whereby:

Further, denoting the distance from the driving face, of any stream line, in the trun= cated areas of pressure, with R the relative Width of the water current, pertaining thereto, is Ra -R and the radius of curva-- ture of the stream line is R-R and therefore, the dynamic pressure p" per unit area, pertaining to the stream line, is

' a Man a a, E Fa l -i n making the" calculations for the location of'the stream lines of equal dynamic pressure, or for ascertainingthe ordinates pressures, for a definite speed N of the pro peller, nor for a medium of a definite density j, because it is suflicient to find the relative values of these pressures, which are practically-constant for any speed or any density of the medium acted upon. The value N r g of Equation Vl is constant for all radii and stream lines of the propeller and there I fore can be left out of consideration in the calculation of the relative value of the dynamic pressures and the equation. may therefore be written: '47t T l-T )R R g P Wa This equation proves that the relative values of the dynamic pressures throughout the areas of dynamic pressure of the water current, are independent of the speed and solely a function of the constructional of the pressurecurves, like those ofFig. VI, a it is not necessary to calculate the actual dimensions of the propeller, namely. the

radius r, the axial pitch T, of the leading edge of the blade and the radii of curvature R, of the driving face lines.

' Fig. 7 is a diagram 10f the dynamic pressures generated by the circular deflection of the Water current throughout of the trancated sector areas of dynamic pressure of the blade sections 3,4, .5, 6, 7, 8, 9 and 10 ofFig. 6. lhe abscissa- 0-3, 0-4, 0-5, etc., to 0-10, on the horizontal base line thereof represent in double the scale of Fig.

(3, the relative Widths of the Water current measured on lines normal to the cross-sectlonal curvature of the dr1v1ng face of the blade, and pertaining to blade sections 3, t, 5, etc., to section 10'. So the horizontal distance, 0-l0 represents the radial dimension 3435; of the truncated sector area of pressure, 33, 34, 35, 36, the horizontal distance 0-9 represents the radial dimension 38-39, of the truncated sector area of dynamic pressure, 37, 38, 39, 40 of Fig. 6, etc.

The vertical'ordinates,0-3, 04, 0-'5, etc., to 0 -10, of Fig. 7, indicate the relative dynamic pressures on the driving, face lines of the blade sections of Fig. 6. The relative values of these pressures are stated in decimal figures at the right of the vertical ordinate 0-10, whereinthe pressure at the line of the driving face of blade section 10 is taken as the unit. The equilateral hyperbolical curves 3-3, 4 l, 5-5, eta, to-

1010,.indioate through the dimension of any'vertical-ordinate which may be drawn of intersectionwith any one of these curves,

from the horizontal base 0 -10 to the pointthe relative dynamic pressures generated within any stream line of the truncated sector' areas of dynamic pressure pertaining to the different blade sections.

In an ordinary propeller in which the a blade cross-sections pertaining to the different radii are located on a line normal to the axis of the propeller, or in which the driving surface of the blade is dished, the outer areas of greater dynamic pressure are located over and overlap the inner areas of.

dynamic pressure of the water current. This is clearly evident in the pressure diagram, Fig. 7, and in the diagram, Fig. 6, in which latter, however, for better understanding of this particular case the blade sections pertaining to the smaller radii must be thought to be. consecutively located under the outer blade section -10, similarly, the truncated sector areas of pressure must be so transferred with the blade sections. In'

a propeller of this description a. considerable'loss of dynamic pressure is caused at the outer radii through the escape of Water at the outer edge of the blade, which, however, in my propeller I completely prevent by providing; the blade at its outer edge with the shrouding 33. 34, 35, 36, equal to the outer area of dvnamic pressure, as shown in Fig. 6; Nevertheless this ,outer '-shrouding increases the efliciencv of the ordinarV propeller only slightly for the reason that the higher pressures maintained at the outer areas of dvnamlc pressure force areas of dvnamic pressure pertaining to the inner radii. and there,'the pressure is inpeller blade, pertaining to the different radii. axiallv, and cireumferentially in such relative positions to each other that the higher pressures at the areas of dvnamic pressure of the outer radii are not located radially outward of the areas of lower. dynamic pressure pertaining to the inner radii. The manner in whi'ch I accomplish this is herewith explained by reference to the diagram. Fig. 7.

In- Fig. 7 the dotted lines 99 e 8, 7-7. etc., to 3-3, are parallel to the base line 0-9*. therefore the point of intersection 9, of line 9-9, with the pressure curve 10-10. is the point of equal pressure, with the point 9, of maximum pressure, of the pressure diagram 0, 9, 9, horizontally to the location 0*, 9, 9, in which the dotted curve 9 -9 represents the pressure curve 9-9, 1t

is clear that the pressure at point 9 is the same for both curves 10-10 and 9-9 and further, it is evident on any other vertical ordinate, for example, on ordinate 41-9, that there the pressure 41-10, pertaining to curve 10-10 or to the outer area of pressure at radius 10, is less than the pressure 41-9, pertaining to curve 9-9, or to the area of dynamic pressure at radius 9 of the propeller. Similar relations of pressure are established between the pressure curves 9-9 and 8-8 by moving the pressure 'diagram 0, 8, 8, to the left, so as to locate point 8, of the ordinate 0-8, on point 8, of the pressure curve 9-9. By shifting of the pressure diagrams O, 7, 7, and 0, 6, 6, etc., in the same way, like relations are established in the pressures of the other diagrams of adjacent radii.

In the diagram, Fig. 8, are shown, in plane development of the co-axial cylindrical sections, the driving faces of the blades, pertaining to radii 3, 4, 5, 6, 7, 8, 9 and 10, of Figs.,1 and 2. Therein, the horizontal axis of rotation, of the propeller, and, at the same time, the axial plane of line 0-10 part of the outer water current toward the. f

Fig. 1. Further, the vertical line Y-Y 0 Fig. 8 indicates a plane, normal to the axis of the propeller and passing through the middle of the driving face ofthe blade section 10. In Fig. 8, the driving faces of the blade sections are shown with their truncated sector areas of dynamic pressure in their correct angular position, in reference to the axis of rotation X-X of the pro peller, and insuch a manner that the middle of the driving face 9'is located on the middle radius of the drivin'gface 10, and further, that the middle of the driving face 8 is located on the middle radius of the driving face 9, etc.,.throughout of the driving faces. Therein, the linear distance 10-9 is equal to the horizontal linear distance of displacement 9-9 of the pressure diagram 0, 9, 9, to the position 0, 9, 9, of Fig. 7,

and the linear distance 9-8, of diagram 8 is equal to the horizontal linear distance of displacement, 8-8 of the pressure diagram 0, 8, 8, of Fig. 7, etc., throughout, of the diagram, Fig. 8. It must' be remembered, however, that the horizontal abscissae, 0-10, 0-9, etc., of .the pressure dia ram, Fig. 7

are shown as twice the scale 0 the Figs. 1

2*, 3, 4, 5, Gand 8 and, that therefore the dimension-lines of displacement, 10-9, 9-8 8-7, etc., of Fig. 8, appear therein only half as long as the corresponding dimension lines 9-9, 88, 7- -7 of Fig. 7. The vertical ordinate, 10-20, in Fig. 8, represents the circumferential componentofthe linear distance 10 -9, or of thedisplacement of the blade section 9, in reference to the blade section 10.

In Fig. 1, the are 1020, is made' of the same length, as the ordinate 1020, of Fig.-

8, and the blade section 9, is located circumferentially, in Fig. 1, by the radial projection of point 20, onto the arc 9-'-19, of the radius 9. 1n the same way, the vertical ordinate 2() 19, of Fig, 8, represents the circumferential component of the linear distance 98, or of the displacement of the blade section 8, in reference to the blade section 9, and, in Fig. 1, the arc919, is made of the same length as the ordinate 2019, of Fi 8, and, the blade section 8,. is located ci cumferentially, in Fig. 1, by,

the radial projection of point 19, onto the 4 arc 818. The blade sections 7, 6, 5, 4: and

, 3, are located circumferentially, in Fig. 1

in like manner, as explained above.

In Fig. 8, the horizontal abscissa "1M9, represents the axial component of the linear distance 109, or of the axial "displacement of the blade section 9, in reference to the blade section 10; likewise the abscissa 4948,

represents the axial component of the linear distance 9-,8, or of the axial displacement of the blade section 8, in reference to the blade section 9. The axial distances of the blade sections shown in dotted lines in Fig.

4:, correspond to the dimensions of the hori- 'zontal absclssae, 1n Fig. 8, wherein the linear.

dimension 10 49, is equal to the axial distance of the blade section 9, from the blade section 10, etc., whereby finally the blade section 3 is axially distant from the blade section 10, Fig. 4, equal to the linear dimension 1 043, of Fig. 8.

Through the diagrams, Figs. 7 and 8 it is evident that the dynamic pressure, at point sures, pertaining to both of the stream lines.

of points 19 and 8, are equal, and therefore, the dynamic pressure, within the stream lines, located radially between any one pair of these points, or within radial-proximity thereof is equal throughout of them, or nearly $9? in this manner, the dynamic pressures, pertaining to the areas ofdynamic pressure, of the dilferent radii, are cated so as to completely prevent centrifug motion of the water current, and thereby the ef- :ficiency of the propeller is materially 'increased. Nevertheless, in the arrangement of the cross sections of the blades described above, the dynamic pressures near the apex of the truncated sector areas of dynamic pressure, are not in perfect radial balance. ,This is apparent in the pressure diagram, Fig. 7, by comparison ofthe pressure curve 1010 of the outer radius 10- of the propeller, with the pressure curve 9-9, of the radius 9. Therein the linear dimension of the vertical ordinate 550, represents the pressure at point 50 of the pressure curve pertainingto the radius 10 of the propeller, and at the same location, the linear dimension of the vertical ordinate 5-42, represents the pressure at point 42, of the pressure curve 99,--at'the radius 9 of the propeller and the linear dimension 5 ().42, in the same location, expresses the difference of dynamic pressure of the stream l nes, pertaining to radii 9 and 10, of the propeller, at this point. This difference of pressure causes part of the water, near the apex OI the pressure areas, to move centrifugally outward, whereby the dynamic pressure at the inner radii is reduced. This deficiency, however,

1 partially avoid, in some cases, by the shifting of the blade sections, of only a fraction of the linear dimension of the lines 9-9, 88, 77*, etc., of Fig. 7, for example, of half of these distances, as indicated, for one instance, by the pressure curve 9"-9", per- I pressure areas is reduced and compensated for by the inward flow of water, near the surface of the blade, where then the dynamic 16o taining to radius 9, which is shifted through pressures, at the outer radii, are slightly greater than at the inner radii. Thereby,

' the water pressures, at the areas of pressure.

of the different radii are very nearly preserved in the condition of radial balance, necessary for the maximum eficiency of the propeller.

1 have found that the performance of propellers is very'materially aifected by slight imperfections of the driving face of the blade, that the latter must be of true 7' form from the leading edge to the rear edge, and that the necessary keenness of theblade'section must be provided for by curves at the back of the blade. This is shown in Fig. 9, in which 51 is the driving face of the blade formed by the draw has its greatest thickness at the rear, between the points 52 and 10, and is made tapering, from the point 10 to the point ,53, from which latter the front cutting edge is formed by the convex-concave curve 533 4, as indicated by the prolongation 54 of the curve, in dotted line. This cross sectional form of the. blade reduces the body resistance thereof considerably without deducting from its strength. The rear edge of the blade is simply formed by the convex curve 83-52.

Fig. 10 shows enlarged a cross section of the shrouding 25 of the propeller, on the line ZZ of Fig. 4:. Therein, the inner face 55 is of true circular curvature from the leading edge 56 to the edge of egress 57 the leading edge being formed on the outside thereof by the concavo-convex curve 5659, as indicated by the dotted line prolongation 58, and the rear edge being formed by the convexcurve 5760. Theouter stationary shrouding 27, of Figs. 1 and 4, servesprincipally as a protector from the disturbing action of side currents, for the purpose of avoiding sudden shocks and vibrations. 'In somecases, for example, under very high rotative speeds or great dynamic pressure, the blades cannot be provided with the shrouding 25, and 'then I make use of the outer stationary shrouding 27, to prevent the radial escape of water from the outer area of pressure.

The propeller principally exemplified herein, has blades with driving faces of a cross sectional curvature, corresponding to a constant multiple of the relative Width of the .water current throughout of the different radii. Further, I have explained my 40 invention b means of a propeller in which the pitch 0 the leading edge, as well as the pitch of egress is constant throughout of the different radii, and likewise I have referred to a propeller with four blades.

5 However, I do not limit my claims to these particular proportions or features, as it is self-evident to those skilled in the arts of engineering that the radii of curvature of the cross sectional lines of the driving face 5 of the blade can be made of any variable,

' instead of a constant multiple, of the relative widths of the water current, throughout of the difierent radii of the propeller,

and further, that the pitch either of the leading edge or the pitch of egress of the blade, or both, may be made to differ throughout of the radii; and that the propeller may ecarried outwith any number of blades, instead of four.

,Inmany cases, it is difficult to make the blades of the propeller sufliciently strong near the hub and at the same time to retain the keenness of the cross section. For that means of steam turbine motors, because it purpose, I considerably increase the pitch of egress, near the hub, as indicated by the 5 dotted lines 55, 56 and 57, of the blade sections 3, 4 and 5, of Fig. 6. Further, in the diagram, Fig. 8, the blade sections are located on a curve 3-10, this, however, is" not a necessary feature of my invention, and 7 in some cases I locate these sections in the plane development of the propeller, either in a straight line or in a line of opposite curvature to that shown in Fig. 8. Further,

I do not limit the claims pertaining to this 7 invention to a propeller with blade cross sections having a concave driving face, be-

cause I have found that blades of true pitch having a straight line driving face in the plane development of the cross section thereof act like blades having a concave driving face and deflect the current in circular stream lines, although imperfectly so.

Having explained the operation of my propeller, in reference to its application for 5 ship propulsion and in reference to its action in water, I do not limit my claims to that purpose, for the reason that, it is advantageously applicable to a great variety of other devices, as flying machines, fans, rotary pumps, air compressors and steam, gas and air turbines, used for the generation of power.

My propeller is very efiicient within a very large range of pitch angles and it can 5 be used with very small pitch angles and high rotative speeds, without a material reduction of its high efficiency. It is particularly suitable for the propulsion of ships, by

can be efliciently'operated under the higher rotative speeds essential for the most economical performance of the latter. Further, my propeller works without pumping action and therefore does not add to the stern resistance of the ship.

I am aware that heretofore, the blades of propellers have been provided with shrouding on the driving face thereof; however, I am not aware that these shroudings have been extended sufiiciently, heretofore, from the driving face of the blade, so as to fully or even approximately cover the area of dynamic pressure pertaining thereto.

It seems that the mechanical principle of 115 the areas of pressure, as disclosed therein, has not been known, or understood, and practically applied in propeller construction heretofore, and I claim particularly asnovel and basic that feature of my invention, which consists in the special selection of the radii of the cross sectional curvature of the driving face-of the blade, for the purpose of augmenting the dynamic pressures of the water current at the different radii of the propeller, so as to establish the radial balante. of the dynamic I the water current.

pressures throughout of Having thus described my invention ll claim as new and desire to secure by Letters to have an area approximately equal to the circumferential area of the water current under dynamic pressure, adjacent to said shrouding.

3. In a rotary propeller, a propeller blade having -.a shrouding on the driving face of the blade, formed of such a size relative to the size of the propeller as to have a surface projecting from the driving face of the blade a distance approximately equal to the Width of the water current under dynamic pressure, adjacentto saidshrouding.

4; In a rotary propeller, a propeller blade curved in a helically pitched spiral of opposite helical andopposite spiral pitch to the pitch of the driving face of the blade. r

5. In a rotary propeller, a blade bent axially in the opposite'direction to the direction of thrust of said bla'de, and also bent circumferentially so as to have the driving face of said blade of convex curvature, and a shrouding member pro ect1ng rearwardly from the outer end of said blade to'a point substantially in line with the base of said blade.

6. In a rotary propeller, a propeller blade curved in a helically pitched spiral of opposite helical and opposite spiral pitch to the pitch of the driving face of theblade, and a shrouding on the driving face of the blade. 1 a

I 7. In a rotary propeller, a propeller blade curved in a helical pitched spiral of opposite helical and opposite spiral pitch to the pitch of the driving face of the blade, a shrpuding arranged with respect to the blade to prevent the radial escape of water from the outer area of dynamic pressure.

8. In a rotary propeller, a propeller blade curved in a helically pitched spiral of opposite helicar and opposite spiralpitch to the pitch of the drivin face of the blade, a shrouding-on the driving face of the blade, and a stationary cylindrical shrouding surrounding the propeller. x

"9. n1 a'rota'ry propeller, a pro eller blade so formed as to have a driving ace of concave curvature in the co-axial cylindrical cross sectional lines thereof, the radii of curvature of which are greater than the radial widths of the'water current area pertaining to each blade section and which are such as to locate, or approximately locate,

the streamlines pertaining to the area ofdynamic pressure of one blade section in radialprojection with the stream lines of equal relative dynamic pressure, pertaining to the .area at d namic vpressure of another blade ,section 0 greater .or less radial distance from the axis of the propeller.

10. In a rotary propeller, a forwardly extending propeller blade and a shrouding member connected to the outer ends of the propeller and extending rearwardly therefrom, said shrouding member being formed of an'area approximately equal to the circumferential area of the water current brought under dynamic pressure by said propeller adjacent said shrouding member.

11. In arotary propellenthe combination with a ring-shaped stationary shrouding member, of a propeller co-acting therewith formed with a blade positioned substantially within said stationary shrouding member and formed with a shrouding member extending parallel to the axis of the propeller.

12. Ina rotarypropellena propeller blade having a driving face of concaved curvature,

' in the coaxial cylindrical cross sectional lines thereof, the radii of curvature of which are greater than the radial width of the water current area pertaining to each blade section and increase from the hub to the outer edge of the blade in such a manner so as to establish or approximately establish in radial projection stream lines of equal relative"dynamic pressure in the areas of dy-- namic pressure pertaining to the cross sectional lines of the drivingface of the blade.

13. In" a rotary propeller, a hub and a blade extending therefrom so formed as to have-a driving face of concave curvature in the co-axial cylindrical cross sectional lines thereof, the-blade being curved circumferentially and axially so as to successively locate or approximately locate the middle of the drivingface lines of the blade cross sections of the lesser radii of the propeller in radial projection of pointsof the radiallines pertaining to the middle of the driving face lines of the blade sections at the greater radii.

14. In a rotary propeller, a hub and extending therefrom a plurality of blades having driving faces of concaved curvature, in

the. co-axial cylindrical cross sectional lines thereof, the radii of curvature of which are greater than the radial width of'the water current areas pertaining to the blade seetionsand increase from thehub to the outer edge of the blade in such a manner so as to locate or approximately locate in radial'projection stream lines of equal relative dynamic pressure in the areas of dynamic pressure pertaining to the cross sectional lines of v the driving face of the blades, the blades being curved circumferentially and axially so as to successively locate or approximately locate, the middle of the driving face lines of the blade cross sections of the lesser constant axial pitch both at the leading edge and the rear edge and so formed as to have driving faces of concave curvature in the coaxial cylindrical cross sectional lines thereof,

the radii of curvature of which are multiples of the radial widths of the cross sectional water current areas pertaining to each blade section and the widths of the blades at the difierent radii of the propeller of which correspond to like multiples of the widths of the ideal blade of least width in which the radii of the cross sectional lines of the driving faceare equal to the radial width of the cross sectional water current areas pertaining thereto and in which the axial pitch of both the leading edge and the edge of egress are1 file same as in the blades of multiple wi t In testimony whereof I have signed my name to this specification in the presence of 

